Set in a fantasy world where humans and vampires coexist, the latter have evolved and no longer rely on human blood as food. Still, they are feared and discriminated against by society, causing many of them to hide their true nature and live as "normal" citizens, or else become outcasts.
Baek Ma-ri (Kim Seolhyun) is a socially withdrawn teenage girl hiding her vampire identity. Driven away from several neighborhoods, she is eager to settle down in her new city and live quietly. But things change when she accidentally kisses the neck of the most popular boy at her high school, Jung Jae-min (Yeo Jin-goo), and falls in love with him.
He is the most popular boy in school. His mother married a vampire when he was in middle school, causing him to quit music. He has hated vampires ever since. He falls for Baek Ma-ri when she transfers to his school, not knowing that she is a vampire.
As a child she was shunned and became an outcast. Determined to graduate from high school, she transfers to a new school and hides her vampire identity. She eventually falls for Jung Jae-min, but is caught in a love triangle with her childhood friend and fellow vampire, Han Si-hoo. She dreams of becoming a musician.
He is a vampire and Baek Ma-ri's childhood friend. His uncle had married Jung Jae-min's mother when he was in middle school. He has feelings for Ma-ri, and becomes involved in a love triangle with her and Jae-min.
She is the most popular girl in school. Used to getting her way, she doesn't like the fact that Baek Ma-ri has captured Jung Jae-min's attention. She resorts to bullying Ma-ri and hiding that fact behind her sweet demeanor.
